package com.xsd.juc;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * @Description: 读写锁
 * @Author: zhoufuzong
 * @Created: 2021-01-02 18:13:24
 * @Version: 1.1.0
 */

class MyCahce{
    private volatile Map<String,Object> map= new HashMap<>();
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();


    public void put(String key,Object value){
        readWriteLock.writeLock().lock();
        System.out.println(Thread.currentThread().getName()+"\t 写入数据"+key);
        try {
            try {
                Thread.sleep(300);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            map.put(key,value);
            System.out.println(Thread.currentThread().getName()+"\t 写入完成");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.writeLock().unlock();
        }


    }

    public void get(String key){
        readWriteLock.readLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"\t 读取数据"+key);
            try {
                Thread.sleep(300);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            Object result = map.get(key);
            System.out.println(Thread.currentThread().getName()+"\t 读取完成"+result);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.readLock().unlock();
        }

    }
}

/** * 多个线程同时读一个资源类没有任何问题，所以为了满足并发量，读取共享资源应该可以同时进行
 *
 * 但是
 * 如果有一个线程想去写共享资源，就不应该再有其他其他线程可以对该资源进行读或写
 * 小总结：
 *      读-读能共存
 *      读-写不能共存
 *      写-写不能共存
 *
 */
public class ReadWriteLockDemo {
    public static void main(String[] args) {

        MyCahce myCahce = new MyCahce();

        for (int i = 1; i <=6 ; i++) {
            final  int tempInt =i;
            new Thread(()->{

                myCahce.put(tempInt+"",tempInt+"");
            },String.valueOf(i)).start();

        };
        for (int i = 1; i <=6 ; i++) {
            final  int tempInt2 =i;
            new Thread(()->{
                myCahce.get(tempInt2+"");
            },String.valueOf(i)).start();

        };

    }
}
